METHOD FOR COMPACTING EXPANDED POLYSTYRENE, AND COMPACTED MASS THUS OBTAINED

Abstract: The invention refers to a method of compacting expanded polystyrene (EPS). EPS, especially in the state of waste, constitutes a problem due to its voluminous nature. High logistic costs are connected with this voluminous nature and therefore it is difficult to realize an efficient recycling of EPS. This invention aims to offer a solution to this logistic problem by transforming the waste EPS in a compacted mass with semi-fluid properties, by bringing the EPS into contact with a liquid that has such a composition that the semi-fluid compacted mass itself is not miscible with the liquid that causes this phenomenon of compacting. To that end the liquid is composed of at least one component with solving power in respect of polystyrene and at least one component without solving power in respect of polystyrene.

Description: METHOD FOR COMPACTING EXPANDED POLYSTYRENE, AND COMPACTED MASS THUS OBTAINED The invention relates to a method of compacting expanded polystyrene (EPS) as well as the processing of the thus obtained compacted mass. EPS is originated from the addition of blowing agents to polystyrene (PS) in order to obtain the PS as a foamed structure : a matrix comprised of fixed or flexible, coherent structural elements of PS that constitute spatial open or closed cells or cavities in which air and/or blowing agents are contained, whether free or entrapped. EPS has found a widespread use : insulation of heat absorbtion of noise, vibration and shocks light-weight-structured material in sandwichpanels and transport packages foamed packaging chips etc. The voluminous nature of EPS, especially in the state of waste, creates a problem in that high logistic costs per ton polymer are involved in handling and transport. A truckload EPS, having a mean density of 25 kg/m , only contains 800 to 1000 kg PS. A reduction of volume, for instance, can be obtained by mechanical means like pressing or treatment between compactor rolls. This type of equipment, especially the roll compactor, is precious and takes relative large amounts of energy to do the job. Especially for the elastic types of foam, mechanical systems are performing less efficient. Furthermore it is difficult to keep polluting blowing agents like CFK 's, present in the older types of EPS, from entering the environment during the compacting process. Methods, among others, are known from the literature in which polymers are being brought into contact with solvents for those polymers. These methods lead to more or less homogeneous solutions of either low or high viscosity, mainly applied as adhesives. DE-C1 3741 777 is related to waste PS that, in contact with solvents, leads to PS solutions with adhesive properties. DE-Al 31 13 125 is related to EPS that, in contact with "stain remover", leads to a solution with adhesive properties. DE-Al 23 03 754 is related to EPS that, in contact with chlorinated hydrocarbons, in particular highly chlorinated hydrocarbons and at higher temperatures, leads to sticky masses with adhesive properties. Based to the present invention is the question how to solve the problem of converting waste EPS in an effective way in a form that, on the one hand, leads to economic advantage by lowering logistic costs related to collecting, handling, storage and transport and, on the other hand, offers the opportunity for reprocessing, whether physically to PS, or chemically to monomer styrene and other raw materials, in that a certain amount of contamination and incompatibility due to the presence of stickerlabels, printing ink, other polymers, adhering sand, organic matter, etc. is not objectionable. It is discovered that the problem can be solved by bringing the EPS in contact with a liquid composed of at least one component with solving power in respect of polystyrene end of at least one component without solving power in respect of polystyrene. Therefore the folowing definitions : 1. The conception "component with solving power in respect of a polymer" : A component has solving power if, in the liquid state, it weakens the bonds between the molecules of a submerged polymer in such a way that these molecules lose their mutual coherence and as a final consequence a one-phase system arises with fluid or semi-fluid properties, in which the molecules are, more or less, homogeneously distributed over the entire system volume. Things to be considered for the temperature range in which the method is applied. In the examples "a component with solving power in respect of polystyrene" is simply referred to as "a solver". 2. The conception "component without solving power in respect of a polymer" : A component has no solving power if, in the liquid state, it is not capable to weaken the bonds between the molecules of a submerged polymer in such a way that thes molecules loose their mutual coherence. What remains after prolonged time is a 2-phase system comprised of an inactive liquid phase and an unaltered solid phase that may be somewhat swollen at the most due to the imbibition of liquid molecules in the polymermatrix. In the examples "a component without solving power in respect of polystyrene" is simply referred to as "a non-solver". It is the embodiment of the invention that by a convenient choice of the composing components and their mutual ratios the liquid obtains the following properties : EPS, contacted with it, shrivels up but does not solve, on the contrary, what arises is a 2-phase system characterized in, on the first side, the existence of a pnlymerphase that is very strongly reduced in volume which phase exists in a semifluid pasteous or dougheous state and that doesn't take up more liquid than necessary for the existence of said phase and, on the second side, the existence of a polymerfree liquid phase that, more or less, keeps the full power of absorbing freshly added EPS in an unaltered fast rate (this in contradistinction to real solvents in which the rate of take-up is fast in the beginning but which rate slows down gradually as the polymerstrength of of the solution increases). Obviously there is a triangular interaction between polymer, solvercomponent(s) and non-solvercomponent(s) : The solver molecules, on the first side, exhibit strong interaction with the polymer molecules, on the second side, they show interactions with the non-solver molecules. The non-solver molecules, however, avoid interaction with the polymer molecules. The stable situation, obviously, is not the homogeneous molecular distribution over the entire system volume but a limitation of the triangular interactions to a part of the systems volume that is as small as possible and that, therefore, has maximum polymerconcentration. In this situation the solver molecules are able to abolish the matrix structure of the polymer enabling said polymer to pass into the liquid state, but, the presence of the non-solver molecules prevents a homogeneous distribution over the entire system volume. The properties of the semifluid polymerphase are adjustable by variation of the ratios of the composing components : At maximum percentage of a solver component the polymerphase has lowest viscosity and to some extent exhibits sticky properties. The heigth of this percentage depends upon the choice of the components that compose the system. In this situation the compacting rate is at a maximum related to the chosen system. At maximum percentage of a non-solver component the polymerphase has highest viscosity but no tendency to stickyness. The height of this percentage depends upon the choice of the components that compose the system. In this situation the compacting rate is at a minimum related to the chosen system. It is always possible to find a working range within those limits in which the polymerphase is optimal in respect of compacting rate, pumpability and tendency for the equipment to become filthy. The position of working range and limits are dependent of the temperature at which the method is carried out. In general at raising temperature there is a shift towards a higher share of non-solver component(s). The invention of the 2-phase system has the following advantages, a. o. : A In respect of the solvent-based systems- 1. The absorbtion of EPS proceeds in an unaltered fast rate from the first up to the last addition. 2. A location for compacting can always be disposed of the compacted polymerphase at its maximum concentration without the need for total consumption of the liquid first. 3. A tank-vehicle can, by pushing aside of phases, with the use of only one tank compartment withdraw the polymerphase and add back the make-up of compacting liquid at the same time and vice versa. 4. A compacting unit is preferably provided with a sieve on which the EPS is dumped. The compacted polymerphase sinks through the mesh while the coarse contaminations remain on top of the sieve without degenerating to a sticky mass. 5. The polymer concentration being at a maximum makes that in the connected processing the amount of liquid to be recovered is at a minimum. 6. The stickyness of the compacted mass being at a minimum is advantageous in the performing of the method, the connected transport and the further processing of the said mass. B. Tn respect of mechanical systems in general. 7. The compacted polymerphase has good pumpability and can be withdrawn from solid contaminations by filtering. 8. Blowing agents, whenever present, can be solved in the polymerphase and thus keep out of the environment. 9. The invention makes possible a wide choice of the composing components, depending upon the market situation in respect of availability of components, the scale of performing the compacting method, the level of fire risk, operative environmental and safety requirements and the kind of the further processing of the compacted mass. 10. The compacted mass is suitable for physical processing to PS as well as for chemical processing to styrene monomer and other chemical materials. 11. By a suitable choice of the composing components of the liquid phase these components can be recovered simply and nearly completely in the processing as aimed at sub 10.. The purport of the invention shall be illustrated in the following examples : (It will be clear that the scope of the invention encloses more than what is made explicit in the examples.) EXΔMELES : Example 1 : Concerns the effect of real solvents in respect of EPS. To 100 gr methylethylketone EPS is added. At first the EPS is absorbed by the liquid in a very fast rate, but, as the concentration of the solution rises the rate of absorbtion slows down progressively. In the end the process stops at 50 - 55 gr EPS absorbed. The highly viscous fluid mass exhibits very sticky properties. Yet from the first addition of EPS there is the origin of only one homogeneous phase of which the viscosity increases the more EPS is added. Comparable effects appear when use is made of, e.g., styrene, toluene, ethylacetate, methylisobutylketone, 1,1,1-trichloro-ethane, etc.. Example 2: Concerns the effect of a liquid comprised of 1 solver and 1 non-solver. Acetone, as it is sold in technical quality, contains some 0.3 % of water. In this case there is the question of a system comprised of acetone being a solver and water being a non-solver. To 100 gr acetone of technical quality EPS is added. The EPS is absorbed in a very fast rate, but, at present no homogeneous solution is obtained but a 2-phase system existing of, on the first side, a compact semifluid polymerphase with highviscous but nevertheless well fluid properties and, on the second hand, a polymerfree liquid phase that is capable to absorb EPS undiminished as fast as before. Since part of the liquid is needed to bring about the fluid polymerphase, the available polymerfree liquid diminishes as addition of EPS continues. As soon as all the liquid is used up, a paste is obtained that contains 85 to 90 gr PS. This amount of PS has not been approached by whatever pure solvent system. Note : The influence of water as a non-solver is extremely strong in this system as will be demonstrated in a later example. Example 3 : Concerns the effect of other liquid systems, also again comprised of only 1 solver and 1 non-solver. 1. To 90 gr methylethylketone 10 gr water is added. EPS is added to the thus obtained liquid. Also in this case EPS is absorbed in the liquid in a fast rate and a 2-phase system is obtained comprised of a semifluid polymerphase and a polymerfree liquid phase, completely analogous with example 2. The total amount of EPS added, 80 to 85 gr, is comparable to the amount as with example 2. 2. Liquid comprised of 25 % methanol (non-solver) and 75 % methylethylketone (solver) : a 2-phase system is obtained : a semifluid polymerphase and a polymerfree liquid phase. 3. Liquid comprised of 25 % methanol (non-solver) and 75 % ethylacetate (solver) : a 2-phase system is obtained : a semifluid polymerphase and a polymerfree liquid phase. 4. Liquid comprised of 85 % dioxane (solver) and 15 % water (non-solver) : a 2-phase system is obtained : a semifluid polymerphase and a polymerfree liquid phase. * Example 4 : Concerns liquid systems comprised of 1 solver and more non-solvers. In al cases a 2-phase system is obtained characterized in a highly concencentrated semifluid polymerphase and a polymerfree liquid phase to which EPS can be added until all liquid is used up. 1. Liquid comprised of 20 % toluene (solver) and 80 % refined spirit (mixture of saturated aliphatic hydrocarbons with boiling range 107 °C to 138 °C, all of which are non-solvers). 2. Liquid comprised of 20 % 1,1,1-trichloro-ethane (solver) and 80 % refined spirit (mixture of saturated aliphatic hydrocarbons, all of which are non- solvers). 3. Concerned is an example that shows that a system component in the pure state does not necessarily has to be a liquid. To 80 gr refined spirit (mixture of non-solvers) is added 20 gr naphtalene (solver) that has been solved in the refined spirit by heating to 50 °C. After cooling to ambient temperature the liquid behaves according the invention. 4. Liquid comprised of 85 % refined spirit (non-solvers) and styrene (solver). Example 5 : Concerned are liquid systems that are composed of 1 non-solver and more solvers. In all case a 2-phase system is obtained characterized in a highly concentrated polymerphase and a polymerfree liquid phase to which EPS can be added continuously until all liquid has been used up. 1. Liquid comprised of 50 % isopropanole (non-solver), 20 % toluene (solver) and 30 % acetone (solver). 2. Liquid comprised of 10 % water (non-solver), 30 % styrene (solver) and 60 % acetone (solver). This example clearly shows how the extremely strong influence of water to the solving power of acetone, as will be shown in - example 7 -, can be forced back by the addition of a second solver with very high affinity towards PS. 100 gr of this liquid absorbs some 70 to 75 gr EPS. Example 6 : " Concerned are systems comprised of more non-solvers and more solvers. All systems are characterized in that 2-phase systems are obtained according to the invention. 1. Liquid comprised of 50 % refined spirit (non-solvers), 30 % acetone (solver) and 20 % toluene (solver). 2. Liquid comprised of 80 % refined spirit (non-solvers) and 20 % Shellsol A (a mixture of hydrocarbons that comprises of aromatics for 98 % and which aromatics all belong to the solvers). Shellsol A has a boiling range from 166 °C to 185 °C. 3. Liquid comprised of 40 % Shellsol A (98 % aromatics, all solvers) and 60 % white spirit D (comprised of highboiling aliphatic hydrocarbons, all non-solvers). White spirit D has a boiling range from 162 °C to 197 °C. Example 7 : Concerns the extreme influence of water (non-solver) in respect of acetone (solver) to the compacting power of this system. 1. Technical acetone contains 0.3 % water. This system has been examined in -example 2 - and it behaves completely according the invention. 2. Acetone whose watercontent is raised to 1.5 %. This system behaves completely according the invention, hardly slower and 100 gr liquid absorbs some 80 to 85 gr EPS. 3. Acetone whose watercontent is raised to 5 %. This system still behaves according the invention but its activity has been diminished to a large extent : its activity is very slow and the obtained semifluid polymerphase has the consistence of a dough that is hardly pumpable. 4. Acetone whose watercontent is raised to 15 %. This system behaves completely inactive. 5. An example, at last, in which the watercontent of technical acetone has been lowered to less than 0.1 % by drying over silicagel. In this case a borderline case has been obtained in which a 2-phase system still appears but the polymerphase has relatively low viscosity now and it also exhibits strong adhesive properties. Besides the polymerphase yet has become relatively transparant as compared to all other systems. Example 8 : Concerns the influence of ratios and temperature in respect of certain systems that are completely composed of hydrocarbons. 1. Shellsol A (mainly solvers) and white spirit D (totally non-solvers), at which only the ratio is examined. In al cases 100 gr liquid absorbs some 90 gr EPS. - 35 % solvers and 65 % non-solvers: The process proceeds relatively slow and the obtained polymerphase exists as a hardly pumpable dough that does not stick. 40 % solvers and 60 % non-solvers : The process proceeds faster and the polymerphase is better pumpable but still exhibits some tendency of stickyness. 45 % solvers and 65 % non-solvers : The system is optimal with respect of compacting rate, pumpability of polymerphase and acceptability of stickyness. 50 % solvers and 50 % non-solvers : The system behaves no longer in accordance with the invention : a homogeneous 1 -phase system is obtained with strong adhesive properties. 2. The system styrene (solver) and refined spirit (non-solvers) : 20 % styrene in refined spirit : the process is extremely fast and the obtained polymerphase has a relatively low viscosity. 10 % styrene in refined spirit : the process proceeds more slowly and the obtained polymerphase is highly viscous. 5 % styrene in refined spirit : the process is very slow and the obtained polymerphase has the consistence of a tough dough. 5% styrene but the liquid heated to 50 °C : the process is as fast as in the case of 10 % styrene and the obtained polymerphase has a viscosity comparable to that case. 3. The system naphtalene (solver) and refined spirit (non-solvers) : 1. 20 % naphtalene and 50 °C : very fast with polymerphase of very low viscosity and highly adhesive. 2. same as 1. and ambient temperature : less fast and strong, yet good pumpable dough with less stickyness. 3. 10 % naphtalene and 50 °C : very fast and better quality paste as with 1. 4. same as 3. and ambient temparature : slow process and tough dough. 5. 5 % naphtalene and 50 °C : fast process and sturdy paste with low stickyness. 6. same as 5. and ambient temperature : very slow process and very tough dough, less useful system to perform the method. Exa ple 9 : In this case a variant of the method is concerned in which a liquid according to the invention and comprised of hydrocarbons is emulgated in water. To a liquid according to the invention, comprised of 20 gr Shellsol A and 80 gr refined spirit, 20 gr oleic acid is added. While stirring this mixture is added to 300 gr water in which sufficient spirit of ammonia is present to build a stable yet non-foaming emulsion. The thus obtained emulsion is more fire-safe then the use of pure hydrocarbon mixtures and also absorbs EPS in that a milky-white homogeneous emulsion is obtained comprised of a countless number of microscopical small systems, that act according to the invention. The milky-white emulsion can be charged with EPS to saturation and nevertheless remains of low viscosity. After charge the emulsion is broken by neutralising the system with diluted hydrochloric acid. After a first coalescence that leads to a separation in a waterphase and an organic phase, the latter again shows a phenomenon of coacervation in that the highly concentrated polymerphase separates from the polymerfree organic phase. This organic phase doesn't absorb any additional EPS and again can be emulgated with water containing ammonia. Apparently the oleic acid molecules with the saturated aliphatics have created a phase that is widely disposed of aromatics. When the aromatic content of this phase is adjusted the emulsion again behaves in accordance with the invention. Example 10 : Concerned is the transport of paste and compacting liquid in one and the same tankcompartment. In general the polymerphases obtained according the invention have a higher density than the compacting liquid itself, causing the semifluid polymerphase to collect at the bottom of a tankcompartment. This fact offers the opportunity to-use only 1 tankcompartment to transport both compacting liquid and polymerphase : A transportvessel, total volume 30 ltrs, is filled with 15 ltrs compacting liquid. Next a collecting tank, having a storage of paste on its bottom, is connected to this vessel and well in such a way that both bottoms are communicating. At that the transportvessel is provided with a so called "floating inlet" that enables the compacting liquid to be transferred by pumping to the collecting tank in that the level of the suction inlet is automatically adapted to the liquid level in the transportvessel. Then the paste in the collecting tank is transferred by pumping to the transportvessel while at the same time a fresh supply of compacting liquid is transferred from transportvessel to collecting tank in an amount that compensates for the liquid withdrawn with the paste Example 11 : Concerns the processing of the obtained compacted mass to PS. 20 kg of the polymerpaste obtained in - example 4, sub 1 - is sucked in by a screwpump and pressed through a filtering unit. Next the mass is transferred to a vacuumchamber by a conveyor screw during which passage the temperature of the mass is raised to over the melting temperature of PS, in order to degas the mass. The sucked off gases are condensed to recover the liquid. Next the degassed polymer is withdrawn from the degassing chamber by an extrusionscrew and processed to granules for injection molding via pressing through a strandforming die. Example 12 : Concerns the processing of the obtained compacted mass to monomer styrene and other chemical materials. To 400 gr technical acetone, 0.5 % water being present in it, is added 360 gr EPS, being the maximum amount the liquid can absorb. 760 gr paste is obtained. From this 570 gr is submitted to pyrolysis, from which 550 gr pyrolysis oil is obtained. By seperation of this oil in a distillation column is obtained : 53 mass % acetone, fit for reuse in accordance with the invention, 23 mass % monomer styrene, 10 mass % other distillates with boilingpoints up to 155 °C and 14 mass % residue with boilingpoints over 155 °C. The thus obtained monomer styrene can be polimerized to clear PS conveniently.

Claims: CLΔIMS : 1 A method of compacting expanded polystyrene in which the expanded polystyrene is brought into contact with a liquid, characterized in, that the liquid is composed of at least one component with solving power in respect of polystyrene and at least one component without solving power in respect of polystyrene, and in which the ratio of these components is such that the liquid compacts the expanded structure and, with the thus compacted polymer, builds a more or less viscous paste or dough that has the property of distinguishing itself from the liquid as a separate and immiscable phase. 2 The method of claim 1, characterized in, that a component with solving power in respect of polystyrene is part of the liquid for at least 1 mass % and for at most 99.9 mass %, which percentage depends upon the choice of the composing compounds and of the temperature at which the method is practised. 3 The method of claim 1, characterized in, that a component without solving power in respect of polystyrene is part of the liquid for at least 0.1 mass % and for at most 99 mass %, which percentage depends upon the choice of the composing components and of the temperature at which the method is practised. 4 The method of claims 1 and 2, characterized in r that one or more components with solving power in respect of polystyrene preferably is (resp. are) chosen from the following classes of chemical compounds : aromatic hydrocarbons constituted of 1, 2, 3 or 4 whether or not condensed benzene rings, as well as homologues whether or not saturated in the side chain. aromatic compounds with substitution in nucleus or side chain, aromatic compounds with keto-, ether- or esterstructure. heterocyclic compounds with one or more oxygen atoms in the ring. alicyclic compounds whether or not with keto-, ether- or esterstructure and wether or not saturated and/or substituted in ring or side chain, aliphatic ketones, ethers or esters. aliphatic unsaturated compounds. halogenated hydrocarbons. The method of claims 1 and 3, characterized in : that one or more components without solving power in respect of polystyrene preferably is (resp. are) chosen from the following classes of chemical compounds : water. aliphatic saturated monohydric alcohols, aliphatic saturated hydrocarbons. The method of claims 1 through 5, characterized in : that the liquid is composed entirely, or almost entirely, of hydrocarbons and in which one or more of the components with solving power in respect of polystyrene is (resp. are) chosen from the class of aromatic and/or alicyclic hydrocarbons while one or more of the components without solving power in respect of polystyrene is (resp. are) chosen from the class of aliphatic hydrocarbons. The method of claims 1,2,3 and 6, characterized in r that the liquid is emulgated in water after which the emulsion is brought into contact with expanded polystyrene that becomes absorbed by the emulsion and by which, afterwards, the emulsion is broken up in order that the pasteous mass becomes separated from the organic liquid phase. The method of claims 1 through 5, characterized in, that the component with solving power in respect of polystyrene is acetone while the component without solving power in respect of polystyrene is water, and in which liquid the water is present for at least 0.1 mass % and for at most 10 mass % but preferably in the range of 0.3 until 3 mass %. The method of the claims 1 through 5, characterized in. that the liquid is composed of more components with solving power in respect of polystyrene, which composition comprises of acetone for at least 50 mass % and of aromatic hydrocarbons for at most 40 mass %, while water, being a component without solving power in respect of polystyrene, is present in the liquid for at least 1 mass %. The compacted mass obtained in the method of one or more of the foregoing claims. The transport of the compacted mass of claim 10, characterized in that in any tankcompartment of the transport vehicle (or transport vessel) a 2-phase system is present consisting of the compacting mass and a liquid of one or more of the foregoing claims. Physical processing of the compacted mass of claim 10 with the aim of obtaining polystyrene. Chemical processing of the compacted mass of claim 10 with the aim of obtaining the monomer styrene and other chemical materials.

Inventors: VAN DEN WITTENBOER JAN, VAN DEN WITTENBOER, JAN
Applicants: WITTENBOER JAN V D, VAN DEN WITTENBOER, JAN
Application year: 1994
Main classification: C08J11
IPC codes: C08J11